Rotary diecutting of web paper products, e.g., to form adhesive labels, is disclosed in U.S. Pat. No. 3,850,059, the disclosure of which is incorporated by reference herein. In diecutting adhesive labels, continuous webs of label material bearing a pressure sensitive adhesive and adhered to a substrate of strippable material is cut while passing through the nip of a rotating die and an anvil or pressure roll. The particular shape or pattern of the label is determined by the shape of the die. The labels are recovered by stripping away the undesired portion of the label material.
Rotary diecutters are expensive pieces of equipment and operate at high speeds and produce large quantities of product in a given time. As a consequence, the dies wear quite rapidly, particularly at their leading edge, and during long runs may require changing, resulting in down time. In addition, it is desirable to use a variety of web sizes and die sizes on the same equipment. Dies of widely differing diameters may be required for different jobs and it may be necessary to process paper webs of varying widths. This necessitates that the diecutting station equipment be equipped to handle varieties of die sizes and paper web widths with equal effectiveness for efficiency and economy.
Diecutting stations which can accommodate different dies are known. It is also known in rotary cutting to apply force to the die to achieve enough contact between the die and the workpiece. U.S. Pat. Nos. 3,491,641 and 3,826,165, the disclosures of which are incorporated by reference herein, disclose typical structures.
Applicant's diecutting structure does not place downward force on the cutting edges of the die except during cutting, thereby extending the life of the die. The die does not place a downward force on the work piece except through the die itself, so the workpiece is not unduly hindered in its travel through the diecutting station. The downward force on the die and diecutting surface is adjustable to insure a continuous cut of good quality throughout the run of the die with a variety of die sizes.
Adjustments and changes in applicant's structure can be made very rapidly with very little time lost through downtime during changeovers or repair. The structure readily accepts dies of different diameters and lengths and will operate on a variety of web widths without major changes in the diecutting station.
The placement of the dies in the diecutting station is readily reversible to allow for longer use of a particular die by getting the maximum cutting from both the front and back edges of the die. The differential wear in the front and back of the die can be accommodated. In many instances this can save the cost of an additional die for a given run or can save the cost of a die of a more expensive design.
The bearings for the die cylinder are free floating, no downward force is applied through the bearings to hold the die in contact with the workpiece, extending the bearing life. The force to the die and die cutting edges is applied close to the diecutting edges so that bending moments along the die cylinder and supporting shafts are reduced. Loads on the die cylinder, die, and other components are supported close to the frame of the machine to minimize stress.